Serum antibodies to surface proteins of as candidate biomarkers of disease: results from the Baltimore Chlamydia Adolescent/Young Adult Reproductive Management (CHARM) cohort.

We previously observed that the nine-member family of autotransported polymorphic membrane proteins (Pmps) of is variably expressed in cell culture. Additionally, -infected patients display variable Pmp-specific serum antibody profiles indirectly suggesting expression of unique Pmp profiles is an adaptive response to host-specific stimuli during infection. Here, we propose that the host response to Pmps and other outer surface proteins may correlate with disease severity. This study tests this hypothesis using an ELISA that measures serum IgG antibodies specific for the nine Pmp subtypes and four immunodominant antigens (MOMP, OmcB, Hsp60, ClpP) in 265 participants of the Adolescent/Young Adult Reproductive Management (CHARM) cohort. More -infected females displayed high Pmp-specific antibody levels (cut-off Indexes) than males (35.9%-40.7% of females . 24.2%-30.0% of males), with statistical significance for PmpC, F and H ( < 0.05). Differences in Pmp-specific antibody profiles were not observed between -infected females with a clinical diagnosis of pelvic inflammatory disease (PID) and those without. However, a statistically significant association between high levels of OmcB-specific antibody and a PID diagnosis (< 0.05) was observed. Using antibody levels as an indirect measure of antigen expression, our results suggest that gender- and/or site-specific (cervix in females . urethra in males) stimuli may control expression in infected patients. They also support the possible existence of immune biomarkers of chlamydial infection associated with disease and underline the need for high resolution screening in human serum.